1. Field of the Invention
The present invention relates generally to fluid measurements and, more specifically, to a fluid measurement system that may be utilized for making mass measurements during fluid flow. The present invention also has application in reduced and zero gravity environments and for finding discontinuities in an otherwise homogeneous material.
2. Background of the Invention
It is well known that when drilling wells for hydrocarbons, a standard drilling practice involves circulating drilling fluid from the surface downwardly through the drilling string. The drilling fluid emerges at the drill bit and returns to the surface through the annulus in the wellbore on the outside of the drilling string. The drilling fluid performs many functions, some of which are discussed herein. The drilling fluid cools and reduces friction of rotating the drilling string. The drilling fluid removes excavated material from the wellbore in the circulation stream flowing to the surface. The drilling fluid is preferably weighted so that a downhole hydrostatic force is created adjacent to hydrocarbon bearing formations, which is greater than the internal pressure within the hydrocarbon bearing if formations. Thus, by adjusting the weight of the drilling fluid with suitable weighting material, blowouts are prevented during the drilling process.
However, due to various conditions downhole, problems may occur with the circulation. For instance, drilling may occur into a lost circulation zone whereby the lost circulation zone, such as a downhole cavern, absorbs a portion of the drilling fluid, thereby reducing the hydrostatic pressure and increasing the potential for a blowout. As another example, drilling may occur into an unanticipated high pressure zone whereby gas bubbles begin to push the drilling fluid out of the wellbore at a higher rate than fluid is pumped into the wellbore thereby reducing the hydrostatic pressure and increasing the potential for a blowout. Surface blowout preventors can be activated to prevent blowouts, but it is highly desirable to have some early warning of impending circulation problems so that suitable pressure control steps can be taken before a blowout actually occurs. It would also be desirable to monitor the drilling fluid density and/or flow rates and/or instantaneous mass in real time with very high accuracy for use in adjusting drilling weights, evaluating formation cuttings, determining changes in drilling such as entry into new formation layers, evaluating drill bit performance in terms of excavated material, and the like, as well as providing early warnings of impending circulation problems.
The following patents listed herein disclose various attempts by previous inventors to solve problems which may be related to the above:
U.S. Pat. No. 4,268,282, issued May 19, 1981, to Cribbs et al., discloses a microwave radar system which employs heterodyned swept frequency at approximately two millisecond sweep intervals. The power source is a reliable solid state, low power device such as a Gunn diode. The heterodyned difference frequency signals are converted to digital form, transformed into the frequency domain by means of a Fourier power transform, and then averaged by computer processing. Performing the Fourier power transform before averaging enables the processing of quasi-incoherent data whereby signal-to-noise ratio improvement is a function of the square root of the average number of samples taken. High-speed processing is used to offset the loss of statistical averaging of phase-coherent data which cannot be preserved because of target motion. Thus, the sequence of the power transform allows phase-less averaging over the entire collection period. Complementary elements including signal isolation and stability, through interdependent design features of the antenna and circulator, permit the use of low-power CW radar which minimizes danger to ecology and human safety. Thus, the invention has particular applicability to the analysis of clouds, the extraction of range and thickness data of clouds, and the presence and velocity of rainfall. The invention can be used for point targets as well. Algorithms are built into the computer to compensate for various factors such as wind, temperature, and the nature of scattering nuclei.
U.S. Pat. No. 4,732,035, issued Mar. 22, 1988, to Lagergren et al., discloses a method and apparatus for substantially eliminating measuring inaccuracies in a storage tank leak detection system caused by temperature-induced volumetric changes in the stored fluid product. In a preferred embodiment of the method, a limp bladder is connected to an end of a pressure tube having an inlet and a substantially hollow core. The pressure tube and the bladder are filled with a medium having a temperature coefficient substantially lower than the temperature coefficient of the fluid product. The pressure tube and the bladder are then supported in a substantially vertical manner in the storage tank such that a first portion of the medium is supported in the bladder in static equilibrium with respect to a second portion of the medium supported in the pressure tube. The large disparity between the temperature coefficients of the medium and the fluid product insures that temperature-induced volumetric changes in the fluid product do not vary the level of the medium in the pressure tube. Accordingly, variations in the medium level in the tube represent a true indication of leakage of the fluid product out of the storage tank or leakage of a foreign product into the storage tank.
U.S. Pat. No. 4,847,623, issued Jul. 11, 1989, to Jean et al., discloses a sweep frequency, continuous wave radar tank gauge providing measurement of the level of tank contents or ullage, having greatly improved accuracy through improved methods of processing calibrate and return signals directed toward the surface of tank contents. Use of sweep synchronous measurement of time domain calibrate/return difference signals and time domain of a virtual xe2x80x9ccarrierxe2x80x9d fundamental in the frequency domain, provide highly accurate measure of tank signal return times. The entire range of return signals is made available for processing and analysis, including distinguishable tank bottom reflections.
U.S. Pat. No. 4,991,124, issued Feb. 5, 1991, to Bruce R. Kline, discloses a method and system that determines the density of a liquid, such as aircraft fuel, by measuring the amplitude of the reflections of ultrasonic pulses from the faces of the walls of a reference material. A transducer is used to transmit an ultrasonic interrogation pulse through a liquid to the reference material. The density of the reference material is known, and its boundaries are well defined. The interrogation pulse is reflected from the faces of the reference material boundaries to provide first, second and third return pulses that can be used to determine the density of the liquid. The density determination is accomplished by determining characteristic impedances, reflection coefficients and transmission coefficients as a function of the returned pulse amplitudes.
U.S. Pat. No. 5,198,989, issued Mar. 30, 1993, to Alan M. Petroff, discloses a sewer flow monitoring system wherein the volume of flow is determined from the depth of fluid in a pipe together with the average velocity of flow through the pipe as determined by detecting the peak velocity from particles flowing in sewage at different velocities and then determining average velocity to be approximately 90% of the peak velocity.
U.S. Pat. No. 5,233,352, issued Aug. 3, 1993, to Thomas C. Cournane, discloses a generation of a first and second identical pseudo-random binary sequences. The second sequence is delayed in a variable delay arrangement, and a reflected first sequence is compared with a delayed second sequence. The second sequence is delayed until the reflected sequence and the delayed sequence are coincident. The delay of the adjustable delay is equal to the travel time of the first sequence.
U.S. Pat. No. 5,315,880, issued May 31, 1994, to Michael R. Bailey, discloses a non-invasive method for measuring the velocity of a fluid surface flowing in a predetermined direction in a channel or flume includes the steps of generating a microwave frequency electrical signal adapted to reflect from the fluid surface; spacing the generation of the electrical signal from the fluid surface; directing the signal along a line toward the fluid surface and opposite the predetermined direction and at an angle of between 30 degrees and 40 degrees to the fluid surface; detecting the signal reflected from the fluid surface; and determining from the directed and reflected signal the Doppler frequency shift therebetween as a measure of the velocity of the fluid surface.
U.S. Pat. No. 5,811,688, issued Sep. 22, 1998, to Marsh et al., discloses a flowmeter utilizing velocity at the surface of a fluid and lookdown level sensors is mounted within a manhole without requiring entry into the manhole by the installer. The velocity and level sensors generate first and second energy signal beams which are directed toward the same vicinity of the fluid surface which reflects the beams back to the sensors surface velocity signal representative of the velocity of scatters on the fluid surface is produced from the Doppler frequency shift between the directed and reflected first beam. This signal is modified to produce a mean velocity signal. A level signal is produced by determining the air space between the sensor and the fluid surface from the directed and reflected second beam and relating changes in the air space to changes in fluid level in accordance with the configuration of the pipe. Fluid flow can be calculated from the mean velocity and fluid level signals.
U.S. Pat. No. 5,942,687, issued Aug. 24, 1999, to Simmonds et al., discloses an aspect of the present invention is an apparatus for inspecting a base of liquid filled tank for corrosion, having (a) a housing for use in the liquid filled tank; (b) a set of one or more ultrasonic transducers mounted to the housing, for directing one or more ultrasonic pulses at the base, where the ultrasonic pulses each have a frequency selected to produce a return signal from the base, and for receiving this return signal; and (c) a data capturing system, for storing information from these return signals. Optional features include a second set of one or more ultrasonic transducers for directing one or more ultrasonic pulses at the liquid/gas interface at a frequency selected to produce a return signal from the liquid/gas interface, a data analysis system, a locomotive system, and a spatial location system. Another aspect of the invention is a method for inspecting a base of a liquid filled tank for corrosion, having the steps: (a) directing a broadband ultrasonic pulse at the base from an ultrasonic transducer within the tank, where the ultrasonic pulse includes a resonant frequency for the tank base over the range of expected thicknesses for the base; (b) receiving a return signal with the ultrasonic transducer; (c) performing a Fourier analysis on the return signal to generate a frequency domain signal; and (d) determining the thickness of the base from the frequency domain signal.
U.S. Pa. No. 6,078,280, issued Jun. 6, 2000, to Perdue et al., discloses a method and apparatus for processing a time domain reflectometry (TDR) signal having a plurality of reflection pulses to generate a valid output result corresponding to a process variable for a material in a vessel. The method includes the steps of determining an initial reference signal along a probe, storing the initial reference signal as an active reference signal, periodically detecting a TDR signal along the probe in the vessel, and computing the output result using the TDR signal and the active reference signal. The method also includes the steps of determining an appropriate time for updating the active reference signal, automatically computing an updated reference signal at the appropriate time, and overwriting the active reference signal with the updated reference signal for use in subsequent computations of the output result.
U.S. Pat. No. 6,097,189, issued Aug. 1, 2000, to Arndt et al., discloses a portable system that is operational for determining, with three dimensional resolution, the position of a buried object or a proximately positioned object that may move in space or air or gas. The system has a plurality of receivers for detecting the signal from a target antenna and measuring the phase thereof with respect to a reference signal. The relative permittivity and conductivity of the medium in which the object is located is used along with the measured phase signal to determine a distance between the object and each of the plurality of receivers. Knowing these distances, an iteration technique is provided for solving equations simultaneously to provide position coordinates. The system may also be used for tracking movement of an object within close range of the system by sampling and recording subsequent positions of the object. A dipole target antenna, when positioned adjacent to a buried object, may be energized using a separate transmitter which couples energy to the target antenna through the medium. The target antenna then preferably resonates at a different frequency, such as a second harmonic of the transmitter frequency.
The above prior art does not disclose a system that provides a highly accurate instantaneous mass determination that may be used for comparing circulation input to the wellbore with the circulation output from the wellbore. Moreover, the prior art does not disclose an inexpensive system for determining densities, volumes, and other measurements of materials such as fluid and water at different positions within a container. Therefore, those skilled in the art have long sought and will appreciate the present invention that addresses these and other problems.
An object of the present invention is to provide an improved fluid measurement system and method.
Another object of the present invention is to provide a highly accurate real time monitor of fluid flow instantaneous mass.
Yet another object of the present invention is to provide a means for measuring the amount (volume) of cryogenic fluids (liquid nitrogen, oxygen, and hydrogen) stored in fuel tanks in zero or reduced gravity environments.
Yet still another object of the present invention is to detect the presence of lumps, variations, and/or other inhomogenuities in materials such as the solid rocket booster (SRB) propellants used in NASA spacecraft.
One of many advantages of the present invention is a highly accurate density measurement.
One of many features of a preferred embodiment of the present invention are novel techniques for accurately measuring total and/or partial fluid flow rates.
Another of many features of a preferred embodiment of the present invention is a system and method to determine fluid density from acoustic phase shift with high accuracy.
An advantage of the present invention is a real time system that permits evaluation of fluid flow for early warning of circulation problems when used in drilling operations.
These and other objects, features, and advantages of the present invention will become apparent from the drawings, the descriptions given herein, and the appended claims. It will be understood that above-listed objects, features, and advantages of the invention are intended only as an aid in quickly understanding aspects of the invention, are not intended to limit the invention or invention definition in any way, and do not form a comprehensive list of such objects, features, and advantages.
Therefore, one embodiment of the present invention comprises a fluid measurement system for a fluid comprising one or more system elements such as, for instance, a detector section defining a fluid channel for receiving the fluid, a sonic detector mounted to the detector section with respect to the fluid channel for transmitting an acoustic signal towards a fluid surface of the fluid within the fluid channel and for receiving an acoustic signal reflection from the fluid surface, and a microwave detector mounted to the detector section with respect to the fluid channel so as to be operable for transmitting a microwave signal towards the fluid surface and receiving a microwave signal reflection from the fluid surface. Thus, the inventive configuration very accurately determines the height of the fluids within the detector section on an instantaneous basis.
Other elements of the system may comprise an instrument section operable for determining a first approximate fluid level of the fluid surface with respect to the fluid channel from the acoustic signal reflection and for determining a second more accurate fluid level of the fluid surface from the first approximate fluid level and the microwave signal reflection. The instrument section may be operable for determining a fluid flow rate of the fluid through the channel from a fluid level of the fluid surface within the fluid channel. In one preferred embodiment, the instrument section is operable for determining the fluid flow rate solely from the fluid level within the fluid channel. In another embodiment, the instrument section detects a phase difference between the transmitted acoustic signal and the received acoustic signal, and the instrument section is operable for determining a fluid density of the fluid from the phase difference.
The system may further comprise a plurality of acoustic sensors mounted to the detector section in communication with the fluid channel. A transmitter acoustic sensor may be provided for producing a transmitted acoustic signal and a receiver acoustic sensor for receiving a received acoustic signal. This configuration can also determine the fluid density at different layers (heights) within the fluid. Multiple transmitter/receiver pairs, each operating at slightly different frequencies may be used to measure the fluid density at different heights through the fluid.
Another embodiment of the invention may comprise a detector section defining a fluid channel for receiving the fluid, at least one acoustic signal transmitter mounted to the detector section in communication with the fluid channel for transmitting an acoustic signal through the fluid, at least one acoustic signal receiver mounted to the detector section in communication with the fluid channel operable for receiving the acoustic signal from the acoustic signal transmitter, and at least one instrument section for determining a density of the fluid from a phase change of the acoustic signal between the acoustic signal transmitter and acoustic signal receiver.
The detector section may define a predetermined physical spacing between the acoustic signal transmitter and the acoustic signal receiver. In one embodiment, the acoustic signal transmitter has an acoustic signal transmission frequency such that a particular 2xcfx80 phase range of the acoustic signal received by the acoustic signal receiver is predetermined. The acoustic signal transmission frequency may be selected such that a maximum phase change for all anticipated densities of the fluid is as close as possible to 360xc2x0 but is preferably at least in the range of from 270xc2x0 to 360xc2x0 to provide for maximum phase sensitivity. Moreover, a frequency adjustment for the acoustic signal transmitter may be provided for selecting an acoustic signal transmission frequency based on a predetermined spacing between the at least one acoustic signal transmitter and the at least one acoustic signal receiver whereby the 2xcfx80 E phase range of the acoustic signal received by the acoustic signal receiver is predetermined.
In another embodiment or variation of the above embodiment, a second acoustic signal transmitter may be mounted to the detector section in communication with the fluid channel for transmitting a second acoustic signal through the fluid such that the second acoustic signal transmitter has a different signal transmission frequency. In this case, the instrument section is operable for determining a particular 2xcfx80 phase range of the acoustic signal utilizing the second acoustic signal.
In operation, a method in accord with the invention comprises one or more steps such as, for instance, transmitting an acoustic signal a predetermined distance through a fluid, receiving the acoustic signal, determining a phase difference of the acoustic signal across the predetermined distance, and determining a density of the fluid from the phase difference.
Preferably, the method comprises determining a 2xcfx80 range (one complete cycle) of the phase difference of the acoustic signal. One method for determining 2xcfx80 range of the phase difference of the acoustic signal further comprises selecting an acoustic signal transmission frequency based on the predetermined distance such that a 2xcfx80 a range is predetermined for an anticipated range of densities of the fluid and/or selecting the acoustic signal transmission frequency and a maximum phase difference of the acoustic signal is preferably less than 360xc2x0 for an anticipated range of densities of the fluid. In another method, the step of determining the 2xcfx80 range further comprises transmitting a second acoustic signal at a second frequency, and utilizing the second acoustic signal for determining the 2xcfx80 range of the phase difference of the acoustic signal. Using more than one acoustic signal frequency allows for the 2xcfx80 phase ambiguities to be resolved over a predetermined density variation.
Another method of the present invention comprises one or more steps such as, for instance, transmitting a microwave signal towards a surface of a fluid to produce a reflected microwave signal, transmitting an acoustic signal towards the surface of the fluid to produce a reflected acoustic signal, and utilizing the reflected microwave signal and the reflected acoustic signal for determining a fluid level of the fluid. Other steps may comprise determining a density of the fluid, and utilizing the density and the fluid level to determine a mass flow rate of the fluid. The step of transmitting the microwave signal may further comprise transmitting a microwave signal that is stepped over a plurality of frequencies and/or processing the reflected microwave signal wherein the processing comprises taking a transform to produce a series of impulse functions.
Higher frequencies with shorter wavelengths allow greater phase resolution and hence increased accuracy in making density measurement. However, there can be 2xcfx80 phase ambiguities, i.e., the number of complete cycles of the transmit signal is unknown. By having additional signals at lower frequencies, and hence, longer wavelengths, allows the number of complete cycles of the signal to be determined. Hence, the 2xcfx80 it phase ambiguities have been resolved and no longer cause ambiguities in the data.
For the particular configuration where both an RF microwave signal and an acoustic signal are used to determine the fluid height within the detector section, the acoustic signal may be used to resolve 2xcfx80 phase ambiguities (number of cycles) for the microwave signal. The measurement accuracy of the microwave signal is much greater than the measurement accuracy of the acoustic signal, but due to the short wavelength of the microwave signal, there can be many 2xcfx80 phase ambiguities for the microwave signal. The acoustic signal is used to resolve these ambiguities.
In a preferred embodiment, a system is provided for measuring fluid mass flow of a drilling fluid circulation stream used while drilling a wellbore with a drilling string wherein the drilling circulation stream is pumped into the drilling string and returns to the surface through an annulus outside of the drilling string. The system may comprise one or more elements such as a sensor housing defining a fluid channel therein wherein the fluid channel is connected within the drilling fluid circulation stream for receiving the drilling fluid from the annulus. Other elements of the system may comprise a first fluid flow rate detector operable for determining a level of drilling fluid within the fluid channel and utilizing only the level for determining a first fluid flow rate through the fluid channel. A fluid density monitor may be mounted within the sensor housing operable for determining a first fluid density of the drilling fluid. At least one instrument section may be provided operable for determining a first fluid mass flow of the drilling fluid from the first fluid flow rate and the first fluid density. In this system, a second density sensor may be positioned along the drilling fluid circulation stream for determining a second fluid density of the drilling fluid in the drilling fluid circulation stream prior to entry into the drilling string, a second fluid flow rate detector positioned along the drilling fluid circulation stream for determining a second fluid flow rate of the drilling fluid in the drilling fluid circulation stream prior to entry into the drilling string, and the instrument section may be operable for determining a second fluid mass flow from the second density and the second fluid flow rate. In a preferred embodiment, the instrument section is then operable for comparing the first fluid mass flow to the second fluid mass flow.
The invention may further comprise another method for determining a velocity of the drilling fluid comprising steps such as receiving a first acoustic signal transmitted through the fluid along a first predetermined path, measuring a first phase change of the first acoustic signal due to a length of the first predetermined path, determining a density of the fluid, receiving a second acoustic signal transmitted through the fluid along a second predetermined path, measuring a second phase change of the second acoustic signal due to a length of the second predetermined path, and calculating the velocity of the fluid from the doppler shift. Secondary acoustic sensors can be installed either downstream, upstream, or both to measure positive and negative doppler shifts from which velocity may be extracted.
An alternate embodiment of the velocity measuring configuration may have additional acoustic transmitter/receiver modules at different heights within the fluid. Thus, the velocity flows for different strata of the fluid can be measured. It is possible that there will be different velocities of the flowing fluid. For instance, fluid flow may vary from slower moving, higher density rock fragments near the fluid stream bottom up to faster moving liquid flows toward the fluid surface. The system of the present invention can measure the velocities throughout the moving fluid.
Yet other embodiments of this measuring system may include multiple acoustic sensors matched to a near steady state flow of a fluid with software algorithms sensitized for detecting minor velocity perturbations riding atop the steady state flow. This configuration could be used to measure velocity perturbations in cryogenic fuel lines feeding liquid oxygen or hydrogen to a rocket engine.
Another embodiment may have multiple transmit/receive sensors mounted to the exterior side of cryogenic fuel tanks in a zero or near zero gravity environment. These sensors would measure the phase shift along paths between the sensors and hence the density or amount of fluid present between the sensors. It is well known that in zero gravity environments, cryogenic fluids tend to flow in globs inside the tanks, making it almost impossible to make measurements as to the amount of fuel remaining in the tank. By having multiple sensors operating at slightly different frequencies, a density profile of the flowing globs of fuel can be measured on an instantaneous basis. Thus, the amount of fuel in the tank can be calculated.
In yet another embodiment, the present invention may involve use of a flexible ring containing multiple transmit and receive acoustic sensors with each sensor pair operating at different frequencies to distinguish the different sensors. A space related application may involve passing this flexible ring along the exterior of long segments of solid rocket fuel propellants to ascertain any anomalies within the usually homogenous propellant tube. These anomalies or lumps in the propellant tube can cause non-uniform firing of the propellant. Any variations in the density of a material can be detected through the very accurate measurement of phase shifts of the acoustic signal as it propagates through the material.